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CHAP, v                 I>R. SEMON'S OBSERVATIONS                     115
grooves in the plates are the remains of the original alveoli of
the teeth.
The Duck-billed Platypus is, as every one knows, an aquatic
animal. It is not found all over Australia, but is limited to the
southern and eastern parts of that continent, and to Tasmania.
The animal excavates a burrow for itself in the bank of the slow
streams which it frequents. The burrow has one opening below
the water and one above; and it is of some length, twenty to
fifty feet. The Platypus feeds upon animal food, chiefly " grubs,
worms, snails, and, most of all, mussels." These it stows away
when captured into its capacious cheek-pouches. The food is
then chewed and swallowed above the surface as the animal
drifts slowly along. Dr. Semon, from whose work, In the
^Australian Bush, this account of the animal's habits is quoted,
thinks that in the nature of the food of the creature the ex-
planation of the loss of the teeth is to be found. He Is of
opinion that for cracking the hard shells of the mollusc Corbicula,
nepeanensis, upon which OrnitJiorJiynchus mainly feeds, the horny
plates are preferable to brittle teeth. OrnitJiorliynclius is appar-
ently not eaten by the natives by reason of its ancient and fish-
like smell. Besides, it is hard to catch on account of its diving
capacities, which are aided by an acute sense of sight and of
hearing. When the Duck-bill was first brought to this
country it was believed to be a deliberate fraud, analogous to
the mermaids produced by neatly stitching together the fore-
part of a monkey and the tail of a salmon.